From: Will Deacon <will.deacon@arm.com>
Date: Mon, 2 Jun 2014 10:47:23 +0000 (+0100)
Subject: arm64: ptrace: change fs when passing kernel pointer to regset code
X-Git-Tag: omap-for-v3.16/fixes-rc4~85^2~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c168870704bcde6bb63d05f7882b620dd3985a46;p=pandora-kernel.git

arm64: ptrace: change fs when passing kernel pointer to regset code

Our compat PTRACE_POKEUSR implementation simply passes the user data to
regset_copy_from_user after some simple range checking. Unfortunately,
the data in question has already been copied to the kernel stack by this
point, so the subsequent access_ok check fails and the ptrace request
returns -EFAULT. This causes problems tracing fork() with older versions
of strace.

This patch briefly changes the fs to KERNEL_DS, so that the access_ok
check passes even with a kernel address.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---

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